I half expected him to be frail, world beaten and weary. He was not.

Sir David Attenborough is standing in a burst of sunshine between storms outside the Australian Museum, looking absolutely radiant. The 90-year-old's cheeks are slightly flushed, his eyes are gleaming and he offers a big, friendly smile to onlookers and earnest fans.

I'm overcome with the urge to hug him, thank him, drop prostrate to kiss his feet... or at the very least look him in the eye and introduce myself.

I have so many questions: What's the secret to his longevity? How damaging can one man, like Trump, be for the environment? Can you call yourself an animal lover if you hate ibis?

But just like that, he's gone.

I'm still slightly out of breath, having raced down four flights of stairs to see him up close. I'd just been to a lunch in his honour at the Australian Museum, and let me tell you everyone in the room was having the best day of their life. Because they were all meeting Sir David Bloody Attenborough.

It's not always a good thing to meet celebrities.

As a journalist, I've had the fortune of meeting -- or at least being in the same room with -- some big names. Snoop Dogg looked old, Princess Kate had a lot of make-up on, Kylie Minogue seemed so very tiny and all politicians pretty much present the same -- a bit shiny, very polite and keen to move on to the next person.

But none of these people are Attenborough.

This is the man who showed multiple generations that the world is vast and wondrous and fragile.

He's the man who inspired us to care about the plight of the fur seal, and then, in a monstrous act of manipulation, got us to also care about the killer whale that eats the seal. By making us empathise with the prey and the hunter, we begin to get an understanding the complexity of an ecosystem. By watching a polar bear searching desperately for a fox to feed her hungry young, Attenborough shows us that no animal is inherently evil, though sometimes homo sapiens make us think twice.

Standing on stage, I half expected him to be frail, world beaten and weary. After all, I'm sure we all know people decades younger who've begun a gentle unwinding into that good night.

Not Attenborough.

He beams. He sways left and right, looking audience members in the eye and gesturing with his arms.

You get the sense he's just another earnest man of science who happens to get to talk about his favourite topic every day -- natural history.

Afterwards, no one screams. Underpants don't rain down on the stage. No one accosts him hoping for a signature, but plenty of earnest men and women of science surround him and he listens like he has all the time in the world.

You get the sense he's just another earnest man of science who happens to get to talk about his favourite topic every day -- natural history.

I'm told he also plonked himself down with a school group and let them ask him questions, prod his tie and sit beside him.

Maybe that's his secret to longevity -- he is present. He listens to everybody. And that's why everybody listens to him.

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